I think there is a lot of people who prefer to re-use as much as possible of what they currently have before they have to throw everything away.. Our current Eth and Wifi shields, to mention two, work with the Due as they are able to detect and adapt to the whatever voltage the main board is operating at.
Making the board 5v tolerant would have made the it way too expensive.
QuoteMaking the board 5v tolerant would have made the it way too expensive. Too expensive for whom?
An audio library for the Due is also being released, coupling onto the Due's ability for wav file playback.